On Tue, Mar 07, 2017 at 01:54:31PM +0800, Qu Wenruo wrote:
>
>
> At 03/07/2017 10:20 AM, Liu Bo wrote:
> > The bug is a regression after commit
> > (da2c7009f6ca "btrfs: teach __process_pages_contig about PAGE_LOCK operation")
> > and commit
> > (76c0021db8fd "Btrfs: use helper to simplify lock/unlock pages").
> >
> > So if the dirty pages which are under writeback got truncated partially
> > before we lock the dirty pages, we couldn't find all pages mapping to the
> > delalloc range, and the bug didn't return an error so it kept going on and
> > found that the delalloc range got truncated and got to unlock the dirty
> > pages, and then the ASSERT could caught the error, and showed
> >
> > -----------------------------------------------------------------------------
> > assertion failed: page_ops & PAGE_LOCK, file: fs/btrfs/extent_io.c, line: 1716
> > -----------------------------------------------------------------------------
>
> We also triggered such bug when running xfstests btrfs/070, although
> possibility is somewhat low.
>
> However since it's more about possibility, any fsstress may trigger it
> though.
>
Yes, I think buffer writes with O_SYNC and some concurrent truncate
could get us to ASSERT.
Thanks,
-liubo
> Thanks,
> Qu
>
> >
> > This fixes the bug by returning the proper -EAGAIN.
> >
> > Cc: David Sterba <dsterba@xxxxxxxx>
> > Reported-by: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> > ---
> > fs/btrfs/extent_io.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index 28e8192..8df7974 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -1714,7 +1714,8 @@ static int __process_pages_contig(struct address_space *mapping,
> > * can we find nothing at @index.
> > */
> > ASSERT(page_ops & PAGE_LOCK);
> > - return ret;
> > + err = -EAGAIN;
> > + goto out;
> > }
> >
> > for (i = 0; i < ret; i++) {
> >
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
